# Audio Stems

> >-

- **Type:** Skill
- **Install:** `agentstack add skill-jagz999-explainer-video-audio-stems`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [JagZ999](https://agentstack.voostack.com/s/jagz999)
- **Installs:** 0
- **Category:** [Content & Media](https://agentstack.voostack.com/c/content-and-media)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [JagZ999](https://github.com/JagZ999)
- **Source:** https://github.com/JagZ999/explainer-video/tree/main/skills/audio-stems

## Install

```sh
agentstack add skill-jagz999-explainer-video-audio-stems
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Audio Stems

Produce a piece's audio as **independent stems** — `voiceover.mp3`, `music.mp3`, `sfx.mp3` — placed on a known timeline, plus an optional ducked `master.mp3`. Delivering stems separately lets you (or the user) iterate on audio **without touching the rendered video**, and drop tracks onto any editor.

## Generate (ElevenLabs — `scripts/elevenlabs.py`)
- **Music bed:** `python3 scripts/elevenlabs.py music "upbeat but understated corporate tech, instrumental, ~120 BPM" music.mp3 --ms 150000`  (caps ~150s; for longer, `acrossfade`-loop). Keep it understated so VO leads.
- **SFX palette:** `python3 scripts/elevenlabs.py sfx "soft cinematic whoosh" sfx_clips/whoosh.mp3 --seconds 0.9` — build a small palette (e.g. `whoosh/swish`, `pop`, `type`, `generate`, `shimmer`, `ding`, `logo`, `crack`). Min duration 0.5s. **Always check level** (`ffmpeg -af volumedetect`); regenerate if `max , "events": [ {"t":12.34,"clip":"whoosh","gain":0.6}, … ] }` (one silent base + each clip delayed to its time), then:
```bash
python3 scripts/build_sfx.py sfx_events.json sfx_clips sfx.mp3
```
Place events at **known choreography moments** — derive them from a scene model or from `vo-sync`'s `timing.json` (`t = scene.start + cue.at`) so a sound lands exactly on the spoken word / the card raise. Same tool builds the VO track if you put per-scene clips in a folder named by id.

## Tasteful placement (learned defaults)
- One **transition** sound (swish/whoosh) per push/scene-change; a softer/low one is less fatiguing than a bright hissy whoosh — offer a few options and let the user pick.
- **pop** on each card raise; **type** while text types, **generate** during a "processing/generating" beat; **shimmer** on a decrypt/sparkle; **ding** on success; **logo** sting on intro/outro; **crack** synced to a fracture.
- Keep per-interaction SFX **quiet** (gains ~0.3–0.5); the SFX track should be mostly silence.
- Don't put events in the 0→first-motion intro; verify every `t ≤ total`.

## Mix (optional master — `scripts/mix.sh`)
```bash
./scripts/mix.sh music.mp3 voiceover.mp3 sfx.mp3 master.mp3
```
Side-chains the music **under** the voiceover (ducks when the voice is present), sums VO + SFX, and limits. Pad/trim every stem to the exact timeline length first (`afade`/`apad`). Target mean ≈ −20 dB, peak < −1 dB.

## Deliver
Hand over the **stems separately** by default (`voiceover.mp3`, `music.mp3`, `sfx.mp3`) — only mux into the video when the user confirms. To mux onto a silent render: `ffmpeg -i video.mp4 -i master.mp3 -c:v copy -c:a aac -b:a 192k -shortest out.mp4`.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [JagZ999](https://github.com/JagZ999)
- **Source:** [JagZ999/explainer-video](https://github.com/JagZ999/explainer-video)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-jagz999-explainer-video-audio-stems
- Seller: https://agentstack.voostack.com/s/jagz999
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.